Rotating heat exchanger drums such as used in the manufacture of paper and fabric utilize rotary joints for establishing communication between the drum and a heating or cooling medium such as steam or cold water. Such rotary joints usually include an elongated pipe or nipple which is concentrically affixed to an end of the heat exchanger drum, and an end of the nipple is located within a chamber defined by the joint housing or body. The pressurized medium communicates with the stationary body and passes through the nipple into the drum. Seal structure within the joint body prevents loss of fluid between the relatively rotating nipple and body. Typical examples of rotary joints for drums are shown in U.S. Pat. Nos. 2,352,317; 2,385,421; 2,700,558; 2,911,234; 3,594,019; 3,874,707 and 4,262,940.
Pressurized fluid mediums, such as steam, impose forces upon the joint seals which accelerate seal wear, and various constructions have been proposed to compenstate for such internal pressures on the seals, and typical examples of pressure compensated rotary joints owned by the assignee are shown in U.S. Pat. Nos. 2,700,558; 3,874,707 and 4,262,940. Rotary joints wherein seal pressures are compensated by externally mounted apparatus, such as in U.S. Pat. Nos. 2,700,558 and 3,874,707 are expensive and bulky, and it is an object of the invention to provide a rotary joint for heat exchanger drums wherein the seals thereof may be internally compensated with respect to fluid pressures and the need for externally located compensating apparatus is eliminated. In the assignee's application No. 739,862 filed May 31, 1985 a double seal internally pressure compensated rotary joint is disclosed, but this rotary joint requires very precise installation and is not self aligning.
Another object of the invention is to provide a rotary joint for heat exchanger drums wherein the seals of the joint are internally compensated with respect to internal pressurized medium forces, the joint may be rigidly mounted, and wherein limited misalignment between the nipple and joint body may be accommodated and the alignment of the joint is automatically achieved.
Yet another object of the invention is to provide a rotary joint for heat exchanger drums wherein the joint seals are internally compensated with respect to fluid pressures, the joint structure may be readily assembled and serviced, and wherein the components may be manufactured by conventional rotary joint machining techniques.
In the practice of the invention a tubular nipple includes an outer end affixed to the end of a heat exchanger drum for rotation therewith, and the nipple inner end is located within a chamber defined within a rotary joint body. The body chamber is partially enclosed by annular wear and assembly plates attached to the body having central openings and inner flat seal surfaces lying in planes perpendicular to the length of the nipple, and annular carbon graphite seal rings engage the plates' seal surfaces. The nipple inner end includes an enlarged cylindrical portion having a collar in the form of a nipple body axially displaced thereon and the nipple body includes a spherical segment seal surface defined thereon engaging a complementary spherical surface on an adjacent seal ring. The nipple body is sealingly axially displaceable upon the nipple inner end enlarged portion and its axial movement is limited by transverse pins mounted on the nipple extending within axially defined slots formed in the nipple body.
A thrust collar having a spherical segment sealing surface is also mounted upon the nipple inner end enlarged portion within the body chamber in sealing engagement with a carbon graphite seal ring associated with the assembly plate and a compression spring is interposed between the nipple body and thrust collar biasing these components away from each other in the axial direction of the nipple. Key pins mounted on the nipple rotate the thrust collar with the nipple.
The geometric relationship and dimensions of the engaging sealing surfaces of the nipple body and associated seal ring, and the thrust collar and associated seal ring, and the faces of these components exposed to the pressure within the chambers are such that the forces imposed upon the nipple body and thrust collar and seal rings within the body chamber are generally balanced preventing excessive axial forces existing between the relatively moving sealing surfaces. In this manner internal seal balancing is achieved.
Ports are defined within the nipple for establishing communication between the interior of the nipple and the joint chamber, and a port within the body communicating with the chamber permits supply of pressurized medium to the nipple. Additionally, a syphon pipe may extend through the nipple and a gland threaded into the thrust collar seals the syphon pipe with respect to the thrust collar permitting communication of the syphon pipe with a head affixed to the assembly plate for permitting steam condensate to be removed from the associated dryer drum.
The desired geometrical relationship between the collars and seal rings can be achieved because of the enlarged cylindrical portion defined on the nipple inner end upon which the collars are mounted. The spherical surface of the nipple body extends over a nipple end transition shoulder and the spherical surface on the thrust collar extends over the nipple terminal end. These relationships permit the outer radial dimension of the collars' spherical surfaces to be greater than the outer diameter of the seal rings and the inner radial dimension of the spherical surfaces of the collars are less than the diameter of the nipple inner end enlarged portion, yet sufficient seal areas of contact between the collars and seal rings is achieved to prevent excessive seal area pressures. The result of these structural and geometrical relationships permits substantial balancing and compensation of the fluid pressures imposed on the collars and seal rings, and in a joint constructed in accord with the inventive concepts seal wear is substantially extended as compared with noncompensated joints. The joint components may be readily assembled within the body cavity and the spherical configuration of seal surfaces of the nipple body and thrust collar permit accommodation of limited misalignment between the body support and the axis of drum rotation while mounting the joint body on a relatively rigid support bracket.